This application relates to a method of machining a part, wherein the length of metal chips removed from the part can be controlled. More particularly, the present invention relates to a method of ensuring that the length of the chips is within a predetermined range.
Machining operations as known in the prior art have problems with chips removed from a workpiece. These chips cause problems if they are overly long, or too short. The chips can clog cutting machinery, which could damage the machinery or cause downtime. Further, long chips can score finished surfaces. Lastly, the chips may be somewhat dangerous to operators.
In response to this problem, attempts have been made to control chip length. One known solution is to periodically apply a high pressure water jet to the chip when it reaches a desired length. This approach has proved unsatisfactory since it does not provide adequate accuracy in chip length.
Another known prior art solution involves the use of a mechanical scribe, which scribes a chip break line into the part. As the part is machined, chips will form from the part until it reaches the chip break line, at which time the chips break off. Mechanical scribes have been unsuccessful for several reasons. First, they are inaccurate in the depth of the chip break line that they cut in the part. Also, the metal on metal contact of the scribe on the part results in undesirable wear. Further, the scribe mechanisms are complicated, too slow, and typically are not adaptable to machine different sized workpieces.
In one disclosed method, a laser beam is moved relative to a workpiece to etch the chip break line into the workpiece. In a disclosed embodiment, the workpiece is rotated while the laser beam is moved radially over the workpiece surface. The laser is preferably mounted on a robot arm which moves about the workpiece. In this way a pattern is formed in the workpiece. By controlling the speed of rotation, the speed of radial movement of the laser and the intensity of the laser, the depth of the break line can be controlled. Further, the size or width of the break line can also be controlled by controlling the various laser variables.
In one disclosed embodiment, a torque convertor housing end plate is machined using the method according to the present invention. It should be understood, however, that the method of the present invention will extend to machining of any known part and particularly including tubular members, or other non-planar parts.
These and other objects and features of the present invention can be best understood from the following specification and drawings, of which the following is a brief description.